Error on reading non-existent property

Usually, an attempt to read a non-existent property returns undefined.

Create a proxy that throws an error for an attempt to read of a non-existent property instead.

That can help to detect programming mistakes early.

Write a function wrap(target) that takes an object target and return a proxy that adds this functionality aspect.

That's how it should work:

let user = {
  name: "John"
};

function wrap(target) {
  return new Proxy(target, {
*!*
      /* your code */
*/!*
  });
}

user = wrap(user);

alert(user.name); // John
*!*
alert(user.age); // ReferenceError: Property doesn't exist: "age"
*/!*

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Error on reading non-existent property

668 B

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